CH712013B1 - Clockwork mechanism with constant force. - Google Patents

Abstract

The constant force clock mechanism according to the invention comprises an input pinion (3); a starter (4) and a driving gear (5); an escape wheel (7); a rotary drive wheel (10) rotatable about a second fixed axis with respect to the first axis; but not to rotate relative to the rotating wheel (8); to be driven by the driving wheel (5); (8) and to drive the escape wheel (7) and the driving wheel stop (10); and at least one abutment (10) and to lock the abutment drive wheel (10) and release it periodically to allow periodic arming of the constant force spring (9). ).

Description

Description: The present invention relates to a timepiece mechanism with constant force.

In a mechanical watch movement, the oscillations of a regulating member are maintained by an escapement which receives a force from a driving spring via a gear train. The force supplied to the exhaust is not constant but varies depending on the winding state of the mainspring. These variations disturb the progress of the regulating organ and therefore reduce the precision of the watch. To remedy this problem, it is known to place an auxiliary spring, known as a constant force spring, in the gear train between the motor spring and the exhaust. This auxiliary spring is periodically armed by the motor spring and drives the exhaust in place of the motor spring. The winding state of the auxiliary spring varies little, so that the exhaust receives a substantially constant force.

For periodic winding of the auxiliary spring, mechanisms that are quite complicated to adjust are generally used, comprising parts such as cam, rocker or anchor. Also known from document CH 709 068 is a constant force mechanism comprising an input pinion intended to be kinematically connected to an energy source and mounted integral with a shaft from which is also secured a planet carrier. On the planet carrier is pivoted a satellite comprising a locking star and a pinion engaged with a fixed wheel coaxial with the shaft. The locking star cooperates with the flat side of a stopper in the form of a half-cylinder secured to an output wheel mounted to rotate freely on the shaft. A constant force spring is fixed between the planet carrier and the output wheel. The output wheel meshes with an escape wheel. The stop, which slides on the teeth of the locking star, periodically releases the latter and therefore the planet carrier to arm the spring with constant force under the action of the energy source. The meshing ratios and the cooperation between the locking star and the stop are determined so that the planet carrier moves in jumps of one second, giving an indication of the dead second type.

Although not using a cam, rocker or anchor, this mechanism according to document CH 709 068 has several drawbacks:

- it is bulky in height. Around the same shaft are in fact mounted the input pinion, the output wheel, the constant force spring, a piton holder (for fixing the constant force spring), the planet carrier and the fixed wheel ;

- The friction between the tip of the teeth of the locking star and the flat side of the stop is high. This friction leads to a significant loss of energy and generates a resistant torque capable of disrupting the running of the watch. In addition, this friction tends to wear out the teeth of the blocking star and therefore to modify the stop point of these teeth on the stop, which affects the display accuracy of the dead second;

- it uses eccentric components which significantly increase the inertia of the assembly, which is all the more annoying that the mechanism is placed near the regulating organ and that it undergoes accelerations and decelerations increased compared to to a conventional clockwork due to the second death.

The present invention aims to remedy, at least in part, the aforementioned drawbacks and to this end proposes a timepiece mechanism with constant force comprising:

- an input gear,

- a mobile arranged to be driven in rotation about a first axis by the input pinion and comprising a stop star and a winding driving wheel,

- an escape wheel,

- a driving wheel rotating stop about a second axis fixed relative to the first axis,

- a winding wheel coaxial with the stop driving wheel but free to rotate relative to the latter, the winding wheel being arranged to be driven by the winding driving wheel,

a spring of substantially constant force arranged to be armed by the winding wheel and to drive the escapement wheel and the driving thrust wheel, and

- at least one stop arranged to be driven by the stop driving wheel and to block the star and release it periodically to allow periodic winding of the spring of substantially constant force.

In the context of the present invention, the term "train" refers to direct or indirect training.

In a preferred embodiment, the input pinion, the stopping star and the winding drive wheel are coaxial and integral (around the first axis) and the escape wheel and the drive wheel. stop are coaxial and integral (around the second axis).

Preferably, the or each stop is secured to a respective wheel arranged to be driven by the stop driving wheel and to rotate around an axis distinct from the first and second axes.

The or each stop may be formed by a portion of a coaxial shaft and integral with said respective wheel.

The or each stop may have a convex flank and a second flank, the convex flank serving as a bearing surface for the teeth of the stop star to block the latter, the second flank serving to release the star d 'stop.

The second side is for example plane or concave.

In an exemplary embodiment, the or each stop is in the form of a half-cylinder.

Preferably, the constant force watch mechanism according to the invention comprises two said stops.

CH 712 013 B1 [0014] According to another advantageous characteristic, the teeth of the stop star are in the form of precious or semi-precious stones secured to a hub.

In an exemplary embodiment, the teeth of the stop star each comprise two flat flanks connected at their free end by a flat surface.

Typically, the spring of substantially constant force is in a spiral.

The outer end of the spring of substantially constant force can be fixed to a stud carried by a coaxial support and integral with the winding wheel, and the inner end of the spring of substantially constant force can be fixed to a shaft on which are mounted the winding wheel, the support and the stop driving wheel and of which is fixed the stop driving wheel.

Preferably, said axes are parallel.

The constant force clock mechanism according to the invention can be arranged so that the stop star is released once per second to allow the indication of a dead second.

The present invention further provides a timepiece mechanism comprising a timepiece constant force mechanism as defined above, a tourbillon cage carrying the timepiece constant force mechanism and a fixed wheel coaxial with the tourbillon cage and meshing with the input gear.

Other characteristics and advantages of the present invention will appear on reading the following detailed description made with reference to the accompanying drawings in which:

fig. 1 to 3 are respectively a plan view from above, a plan side view and a perspective half view of a constant-force watch mechanism according to a preferred embodiment of the invention;

fig. 4 is a schematic top view of a stop star and stops forming part of the constant-force timepiece mechanism according to the preferred embodiment of the invention;

fig. 5 and 6 are respectively a plan view from above and a plan side view of the constant-force watch mechanism according to the preferred embodiment of the invention on board a tourbillon cage.

Referring to Figs. 1 to 3, a constant force watch mechanism 1 according to the invention, intended to be part of a watch movement such as a wristwatch or pocket watch movement, comprises, around a first shaft 2 d axis A, an input pinion 3, a stop star 4 and a winding driving wheel 5. These three coaxial elements 3, 4 and 5 are integral with the shaft 2. The input pinion 3 receives a force from an energy source, typically a barrel, from movement. The stop star 4 comprises teeth 4a advantageously constituted by precious or semi-precious stones (natural or synthetic), typically ruby, sapphire or garnet, embedded in a hub 4b. Teeth 4a have a shape similar to exhaust anchor paddles. They thus comprise (cf. fig. 4) two parallel sides 4c connected at their free end by an inclined face 4d. The teeth 4a are regularly distributed around the hub 4b. In the example shown, there are four of them. Their radial position relative to the hub 4c can be adjustable.

The constant force clockwork mechanism 1 further comprises, around a second shaft 6, the axis B of which is distinct from the axis A and parallel and fixed relative to the latter, an escape wheel 7, a winding wheel 8, a constant force spring 9 in the form of a spiral and a stop driving wheel 10. The escape wheel 7, the inner end, designated by 9a, of the constant force spring 9 and the wheel stop driver 10 are integral with the shaft

6. The winding wheel 8 is integral with a support 11 mounted to rotate freely around the shaft 6. This support 11 carries a peg 12 to which is fixed the outer end, designated by 9b, of the constant force spring 9. The escape wheel 7 cooperates with an escape anchor which itself cooperates with a regulating member, typically a balance spring, in a conventional manner.

The winding wheel 8 meshes with the winding driving wheel 5. The stop driving wheel 10 meshes with one or two (two in the example illustrated) mobile stop each rotating about a separate axis C axes A and B and parallel and fixed with respect to the latter. Each stop mobile comprises a wheel 13 and a shaft 14 around which the wheel 13 is mounted integrally. The wheel 13 is engaged with the stop driving wheel 10. A portion 15 of the shaft 14 constitutes a stop in the form of a half-cylinder whose cylinder axis coincides with the axis C. Each stop 15 thus comprises (cf. fig. 4) a flat side 15a and a cylindrical side 15b. The stops 15 have the function of blocking the star 4 and releasing it periodically.

In operation, the constant force spring 9 drives the escapement wheel 7 which moves in a jerky manner according to the alternations of the regulating member. This movement of the escapement wheel 7 rotates, via the stop driving wheel 10, each stop mobile 13, 14 and therefore each stop 15. As shown in FIG. 4, the stop star 4 remains blocked by one, 15 ′, of the stops 15 against which one of the teeth 4a ′ rests, until the plane flank 15a of the stop 15 'is in front of the end of tooth 4a', allowing tooth 4a 'to pass and

CH 712 013 B1 therefore to stop star 4 to be released. Under the action of the movement's energy source, the mobile comprising the shaft 2, the input pinion 3, the stopping star 4 and the winding driving wheel 5 rotates until another tooth 4a of the stop star 4 comes to rest against the other stop 15. During this movement of the mobile 2 to 5, at an angle of 45 ° in the example illustrated, the winding wheel 8 is driven which arms the spring of constant force 9. Preferably, the release of the stop star 4 occurs every second so that the jumps of the mobile 2 to 5 can be used to cause a dead second indicator.

The force required to drive the escape wheel 7 is thus always provided by the constant force spring 9 and not by the power source of the movement, so that it does not depend on the state of arming of said energy source.

The mechanism according to the invention is of simple design. It does not use parts such as cams, anchors or rockers for the periodic winding of the constant force spring. It also does not require precise adjustment. In addition, it is compact in height because its components are distributed in a substantially balanced manner around the axes A and B.

Another advantage of the mechanism according to the invention is that it produces little friction. As already indicated, the teeth 4a of the stop star 4 are made of precious or semi-precious stone such as ruby, sapphire or garnet, that is to say a material which reduces friction. In addition, as can be seen in FIG. 4, the function of the planar blank 15a of each stop 15 is to bring the stop 15 out of the path traversed by the teeth 4a to let a tooth 4a pass and release the stop star 4. The teeth 4a are never in contact with this flat side 15a. Throughout the duration of the stopping of the stopping star 4, the contact takes place between a flat flank 4c of a tooth 4a and the cylindrical flank 15b of a stop 15. Any contact points on flank is therefore avoid. In addition, as each stop mobile 13, 14 rotates on itself, around the fixed axis C, the moment of the frictional force exerted by a tooth 4a in contact with a stop 15 is low. The lever arm in fact corresponds to the radius R of the cylindrical flank 15b, a radius which is much smaller, for example the distance between the axis B and each stop 15.

In variants, one could give the sidewall 15b other convex shapes than a cylindrical shape, for example a spherical or barrel shape. Instead of a planar shape, the flank 15a could have a concave shape. Yet another advantage of the mechanism according to the invention consists in the fact that it is not very sensitive to manufacturing tolerances. Indeed, between the penultimate step of a stop mobile 13, 14 where the stop star 4 is still blocked and the last step where the stop star 4 is released, the angle of rotation of the stop mobile 13, 14 can be relatively large, by 20 ° in the example illustrated. Such an angle of rotation offers great robustness in terms of the accuracy of displaying the dead second.

The mechanism according to the invention can easily be loaded into a tourbillon cage. By “tourbillon” is meant in the context of the present invention any rotating regulating system including the actual tourbillons and the carousels. Figs. 5 and 6 show an exemplary embodiment of the mechanism 1 according to the invention mounted in a tourbillon cage 16. The shafts 2, 6 pivot in the cage 16, and the cage 16 also carries an escape anchor 17 with which the escapement wheel 7 and a regulating member (not shown) with which the escapement anchor 17 cooperates. A second pinion 18 coaxial and integral with the tourbillon cage 16 is driven by the energy source of the movement via a finishing cog. The input pinion 3 meshes with a fixed second wheel 19.

Thus, each release of the stop star 4 by the stops 15 causes a displacement jump of the tourbillon cage 16. The latter can carry a second hand and thus constitute a dead second indicator.

The present invention has been described above by way of example only. It goes without saying that modifications could be made without departing from the scope of the claimed invention. For example, the input pinion 3 could not be coaxial with the mobile comprising the stop star 4 and the winding driving wheel 5 but could mesh with the winding driving wheel 5 to drive said mobile. Another modification could consist in moving the escape wheel 7 so that it is no longer coaxial with the winding wheel 8 and the driving drive wheel 10 and that it forms part of a mobile which would mesh, and would be driven by, the stop driving wheel 10.

Claims (16)

claims 1. Constant force watch mechanism comprising: - an input gear (3), a mobile arranged to be driven in rotation about a first axis (A) by the input pinion (3) and comprising a stop star (4) and a winding driving wheel (5), - an escape wheel (7), - a stop driving wheel (10) rotatable about a second axis (B) fixed relative to the first axis (A), - a winding wheel (8) coaxial with the stop driving wheel (10) but free to rotate relative to the latter, the winding wheel (8) being arranged to be driven by the winding driving wheel (5) a spring of substantially constant force (9) arranged to be armed by the winding wheel (8) and to drive the escapement wheel (7) and the stop driving wheel (10), and CH 712 013 B1 - at least one stop (15) arranged to be driven by the stop driving wheel (10) and to block the star (4) and release it periodically to allow periodic winding of the spring of substantially constant force ( 9). 2. A constant force clockwork mechanism according to claim 1, in which the input pinion (3), the stop star (4) and the winding driving wheel (5) are coaxial and integral. 3. Constant force watch mechanism according to claim 1 or 2, in which the escapement wheel (7) and the stop driving wheel (10) are coaxial and integral. 4. Constant-force watch mechanism according to one of claims 1 to 3, in which the or each stop (15) is integral with a respective wheel (13) arranged to be driven by the stop driving wheel (10) and to rotate around an axis (C) distinct from the first and second axes (A, B). 5. Constant-force watch mechanism according to claim 4, in which the or each stop (15) is formed by a portion of a shaft (14) coaxial and integral with said respective wheel (13). 6. Constant force timepiece mechanism according to one of claims 1 to 5, in which the or each stop (15) has a convex flank (15b) and a second flank (15a), the convex flank (15b) serving as a surface. supporting the teeth (4a) of the stop star (4) to block the latter, the second flank (15a) serving to release the stop star (4). 7. Constant force watch mechanism according to claim 6, in which the second flank (15a) is plane or concave. 8. Constant force watch mechanism according to one of claims 1 to 7, wherein the or each stop (15) is in the form of a half-cylinder. 9. Constant force clockwork mechanism according to one of claims 1 to 8, comprising two said stops (15). 10. Constant-force watch mechanism according to one of claims 1 to 9, in which the teeth (4a) of the stop star (4) are precious or semi-precious stones secured to a hub (4b). . 11. Constant force clockwork mechanism according to one of claims 1 to 10, in which the teeth (4a) of the stop star (4) each comprise two flat sides (4c) connected at their free end by a surface. plane (4d). 12. Constant force watch mechanism according to one of claims 1 to 11, in which the spring of substantially constant force (9) is in a spiral. 13. Watch mechanism with constant force according to claim 12, in which the outer end (9b) of the spring of substantially constant force (9) is fixed to a stud (12) carried by a support (11) integral with the wheel d 'armament (8), and wherein the inner end (9a) of the spring of substantially constant force (9) is fixed to a shaft (6) on which are mounted the winding wheel (8), the support (11 ) and the stop driving wheel (10) and of which the stop driving wheel (10) is integral. 14. Constant force watch mechanism according to one of claims 1 to 13, wherein said axes (A, B, C) are parallel. 15. Constant force clockwork mechanism according to one of claims 1 to 14, arranged so that the stop star (4) is released once per second to allow the indication of a dead second. 16. Watch mechanism comprising a constant force watch mechanism (1) according to one of claims 1 to 15, a tourbillon cage (16) carrying the constant force watch mechanism (1) and a fixed wheel (19) coaxial with the tourbillon cage (16) and meshing with the input pinion (3). CH 712 013 B1

CH 712 013 B1